Build a community garden. This is a time-tested way to promote community interaction in your neighborhood as well as share in a bounty of fresh veggies. Check out the American Community Gardening Association’s steps for getting started.

If you already have a community garden, then examine it to see if you could make any improvements. Is it accessible to everyone? If not, think about how you could add or change features to fix that. You don't have to make the entire space accessible as long as people can get into it easily and do all the things somewhere. Alternatively, you could create a new community garden in another space that is fully accessible, which lets you do creative things -- such as putting roll-under beds above an abandoned parking lot -- that wouldn't be compatible with extant hardscaping.

The same goes for other alternative or specialized approaches. Organic gardens, vertical gardens, perennial gardens, and permaculture gardens, are all things that people sometimes squabble over in conventional community gardens. Give them their own spot and you not only solve that problem, you also reduce crowding and create multiple locations to spread out the benefits of green space. As with accessibility, some places unsuitable for ordinary gardens are preset for alternatives -- any sturdy old building becomes a frame for vertical garden, and so on.